Fish Physiology and Biochemistry最新文献

Shabout is a fish with high nutritional value and economic potential. This fish is exposed to environmental factors due to the metal toxicity in its habitat and, consequently, its diet. The main purpose of this study was to determine how the detoxification mechanism of shabout is affected by examining the interaction of glutathione s-transferase enzyme with heavy metals. In our study, elemental analysis was first performed with the ICP-OES on water samples taken from three different points to detect metal toxicity in the habitat of the shabout. Then, the GST enzyme from the liver tissue of the shabout was purified for the first time by our team using the glutathione agarose affinity chromatography technique. Finally, the inhibition effects of nitrate salts of some metal ions on the purified enzyme activity were investigated under in vitro conditions. It was determined that the water courses where the fish were sampled in our study were alarming in terms of heavy metal content. While shabout liver showed Fe³⁺ activation effect on GST enzyme under in vitro conditions, metal ions Na⁺, Zn²⁺, Co²⁺, Cu²⁺ and Pb²⁺ showed inhibition effects. The detected inhibition concentration range showed that the enzyme is quite resistant to the metal salts whose effects were examined. It was concluded that in the consumption of shabout, emphasized to be a nutritious fish, the heavy metal levels of the region where the fish is caught should be taken into account and catching should be made in water resources inspected by relevant experts.

The acclimation response of fish gills to chronic intermittent hypoxia (CIH) is an important aspect to understand, as anthropogenically induced hypoxia in water bodies has been a stressor for fish for many years and is expected to persist in the future. In order to investigate the acclimation response of fish gills to CIH stress, we conducted a study using largemouth bass (Micropterus salmoides) exposed to intermittent hypoxia (dissolved oxygen level, 2.0 mg·L^-1) for either 1 or 3 h per day, over a period of 8 weeks. Our findings indicate that exposure to CIH induced remodeling of the gills and an increase in gill surface area. This remodeling of the gills may be attributed to changes in cell growth and proliferation, which are influenced by the activation of the MAPK signaling pathway. We also observed significant upregulation of genes related to glycolysis (fba, pgam1, pepck, atp-pfk, pfk-2, g6pi, gapd-1, and pk), while genes associated with cholesterol synthesis (3β-hsd, cyp51, dsdr- × 1, dsdr, and dhcr7) were downregulated following CIH exposure. Furthermore, we observed the presence of elongated megamitochondria in mitochondria-rich cells within the gills of fish exposed to hypoxia. Additionally, numerous genes involved in calcium signaling pathways were upregulated in the gills of largemouth bass, suggesting an enhanced sensitivity of gills to environmental cues in hypoxia conditions. However, the expression levels of certain genes related to innate and adaptive immune responses were inhibited following CIH exposure. Moreover, the number of mucous cells decreased after CIH exposure. This may have made the gills more susceptible to infection by pathogens, although it facilitated oxygen uptake. These findings highlight the potential vulnerability of gills to pathogenic organisms in the presence of CIH. Overall, our study contributes to a better understanding of how fish acclimate to CIH.

The primary function of spermatozoa is to fertilize the oocyte, which depends on their motility and is directly associated with their metabolic state. The oxygen consumption rate (OCR) of spermatozoa reflects the respiratory capacity of sperm mitochondria under various physiological conditions and is an essential marker of sperm quality. We determined the OCR of common carp (Cyprinus carpio) sperm using two respirometry methods: the conventionally used polarographic method with a Clark-type electrode and fluorometric assay with an Oxo Dish optochemical oxygen sensor. The latter was used for the first time to evaluate spermatozoa oxygen consumption in various metabolic states (under different treatments) at different dilution rates. These two methods were compared using Bland-Altman analysis, and the applicability of the optochemical oxygen sensor for evaluating carp sperm oxygen consumption was discussed. Sperm motility and progressive velocity parameters were also assessed to evaluate the effect of sperm respiration under different metabolic states and dilution rates and preincubation period on the physiological status of spermatozoa. The comparison of these respirometry methods clearly shows that while the polarographic method allows immediate measurement of oxygen levels after adding a sperm sample, the optochemical oxygen sensor has a priority in the amount of data obtained due to simultaneous measurements of several samples (e.g., different males, different fish species, repetitions of the same sample or various experimental conditions), even at a later time after adding sperm to the measuring chamber. However, the compared methods are complementary, and the proposed methodology can be applied to other fish species.

Trophic factors, such as neurotrophins, are fundamental for cellular processes including differentiation, growth, survival, and regeneration. These molecules exhibit significant morphological and phylogenetic conservation throughout the animal kingdom, indicating conserved functions. In fish, the oldest and most diverse group of vertebrates, neurotrophins, and their receptors play pivotal roles not only within the central nervous system but also in various peripheral tissues. They are distributed in mechanosensory, muscle, skin, respiratory, circulatory, digestive, endocrine, urinary, reproductive, and immune systems, suggesting their involvement in the development and maintenance of all tissues/organs/systems. Despite this broad distribution, studies focusing on these molecules outside of the central nervous system have been limited to just 12 fish species. These investigations have revealed diverse expression patterns across different ages and tissues/organs/systems, expanding our comprehension of their functions beyond the central and peripheral nervous systems. Notably, BDNF and NT-3 are prominently expressed outside the central nervous system, particularly in mechanosensory and digestive tissues, whereas NGF is predominantly observed in mechanosensory and urinary systems. The expression and localization of neurotrophins and their receptors vary among organs, underscoring tissue-specific roles. Further research is imperative to decipher the precise functions and mechanisms of action of neurotrophins and their receptors in diverse fish tissues. Enhanced efforts are needed to include a broader range of fish species in these studies to advance our understanding of these agents in complex vertebrates, thereby shedding light on tissue development, regeneration, and maintenance, with potential implications for addressing organ-related issues.

Under low O₂, the heart of Carassius auratus (goldfish) shows an enhanced hemodynamics. This is observed in ex vivo cardiac preparations from animals acclimated to both normoxia and short-term (4 days) moderate hypoxia and perfused for 90 min with a hypoxic medium. Under short-term hypoxia, this is associated with a higher ventricular muscularity and an expanded mitochondrial compartment. To date, little is known about the putative influence of hypoxia on the mitochondrial contribution to cardiac energy metabolism. Similarly, it remains unexplored whether the exposure to environmental low O₂ affects the cardiac response to preload increases (i.e., the Frank-Starling mechanism). We here observed, on ex vivo isolated and perfused goldfish heart, that 20 days of exposure to moderate water hypoxia are accompanied by a potentiated cardiac performance, analyzed as stroke volume, cardiac output, and stroke work. The sensitivity to preload increases significantly improved after 20 days of hypoxia, while it is similar to normoxia after 4 days of exposure. This suggested a time-dependent response. Mitochondrial O₂ consumption initially decreased during short-term hypoxia but returned to normoxia-like levels after 20 days of exposure. Biomolecular analyses of ventricular extracts revealed a time-dependent regulation of key proteins involved in the mitochondrial biogenesis, including PGC1α, NRF1/2, and TFAM, as well as cytochrome c. Additionally, mitochondrial DNA content was notably increased after 20 days of hypoxia. Our data revealed that, when challenged by chronic environmental hypoxia, the goldfish heart improves its pumping behavior under both basal and loading-stimulated conditions. This is accompanied by a mitochondrial remodeling which likely supports adequate energy supply for the working myocardium.

The effect of different feeding habits on gut morphology and digestive function has been intensively studied during the last decades but sympatric closely related fishes are relatively rare objects of such studies. In the present study, we have identified both morphological and physiological changes in the digestive system of a sympatric pair of whitefish represented by "normal" Coregonus lavaretus pidschian (benthivorous) and "dwarf" C. l. pravdinellus (planktivorous) forms. There were statistically significant differences in terms of histometric variables between segments of the stomach (height of lining epithelium, fold thickness and height values, and number of folds) and intestine (enterocyte height and fold height) within each form as well as between forms for the same segment of the digestive tract like in the stomach (height of lining epithelium and fold thickness) and intestine (enterocyte height, fold height and fold thickness). Both forms had a similar number (8-9 bands) and molecular weight of isoforms/isoenzymes of alkaline proteases inhibited by PMSF (serine proteases) based on zymogram analyses. The maximum level of activity of alkaline proteases, alkaline phosphatase, and aminopeptidase N were registered in the pyloric caeca for both forms. In contrast to these enzymes, the activity of α-amylase as well as of non-specific lipases and esterases in the pyloric caeca was similar or even lower if compared to other intestinal segments. In conclusion, both sympatric forms of whitefish showed some similarities in several of studied biochemical and histological parameters of their digestive tracts, regardless of their different feeding habits, which might be related to their genetical background.

Oxytetracycline (OTC), an approved antibiotic for aquaculture, is under strict control and regulatory endeavour. This study compared the effects of oral administration of graded doses of OTC comprising the therapeutic (80 mg/kg biomass/day), subtherapeutic (40 mg) and overdoses (240, 400 and 800 mg) in male Nile tilapia Oreochromis niloticus fries (0.64 ± 0.02 g) when fed for 10 consecutive days and observed for 22 days post-OTC-dosing (POD) period. A dose-dependent reduction in food intake, survival and muscle calcium, chloride, malondialdehyde and superoxide dismutase was observed, while the muscle glucose significantly increased. However, the changes were reversible with dose cessation. The fries of the therapeutic dose group recorded the maximum biomass, while the overdosed groups recorded a significant decline in weight gain. On day 10 of dosing, all groups' muscle OTC residues peaked. The residues in the subtherapeutic and therapeutic dose groups were lowered below the maximum residue limit (MRL) of 100 ng/g on day 10 POD. The residues were further reduced close to the MRL in the overdosed groups on day 22 POD. The fries tolerated the therapeutic dose well and showed effective adaptive responses. Considering muscle residue accretion and physiological responses, OTC can be endorsed as a safe drug for in-feed administration to tilapia fries. However, the sensible use of this approved drug is essential for sustainable aquaculture.

The target of this novel work is to assess the immunosuppression, genotoxicity, histopathological alterations, and cumulative mortality induced by acute toxicity of magnetite nanogel (MNG) in Nile catfish. Furthermore, a subsequent 10-day depuration period is adopted to estimate the restoration of those disturbed indices. Nile catfish (n = 180) were allotted into four groups and exposed to different concentrations of MNG (0, 1/10, 1/8, and 1/5 96-h LC₅₀). The outcomes displayed a remarkable concentration-dependent decline in the immune indices level (LYZ, NO, and MPO). The gene expression of antioxidant (SOD) and apoptosis-regulatory genes (MAPK3 and JNK) was upregulated in MNG-exposed fish. Histopathological disruptions in the tissue architecture of gills and intestines were also evident in MNG-exposed groups. Interestingly, after a 10-day depuration period, marked improvement in the level of immune response mediators and gene expression of apoptotic genes was evident in all experimental groups, particularly at 1/10 of LC₅₀. Overall, exposure to higher concentrations of MNG (1/5 and 1/8 of LC₅₀) exerts multiple adverse influences on the Nile catfish, which were less pronounced at 1/10 of LC₅₀. Surprisingly, a subsequent 10-day recuperation time was adequate for alleviating those impairments, with the maximum improvement in the Nile catfish exposed to 1/10 of LC₅₀.

Pituitary gland morphogenesis and the ontogeny of the adenohypophyseal (AH) cells of Astyanax lacustris are presented herein. This Characiformes species shows great ecological and commercial importance, and it has been increasingly used as animal model. For this study, A. lacustris specimens were collected from 0.5 to 120 days after hatching (dah) (adults). The entire animal or its head was appropriately fixed, and after histological processing, the sections were subjected to histochemical and immunohistochemical reactions, using homologous and heterologous antibodies. The first AH cells of A. lacustris were detected at 1 dah by the immunostaining of prolactin (PRL)-producing cells. The morphology of the gland presented changes in shape throughout the development, starting with elongation but more oval at the end. The neurohypophysis was differentiated at 3 dah, along with the identification of adrenocorticotropic hormone (ACTH), melanotropic hormone (MSH), thyroid-stimulating hormone (TSH), and follicle-stimulating hormone (FSH)-producing cells. Identification of the immunoreactive cells to anti-luteinizing hormone (LH), anti-somatolactin (SL), and anti-growth hormone (GH) antibodies occurred at 5 dah. At 20 dah, an increase in pituitary proportions and the presence of the pituitary stalk were observed. At 60 dah, the pituitary gland already had the same shape and distribution of AH cells seen in the adult. The ontogeny of adenohypophyseal cells in A. lacustris corroborates the heterogeneity in the appearance of these cell types in teleosts and suggests that these hormones actively participate during the post-hatching development of this species, even before the establishment of all endocrine axes. Our findings contribute to understanding the morphogenesis of the hypothalamic-pituitary axis in South American teleosts, providing essential data for the development of future studies related to pituitary gland morphophysiology under normal or experimental conditions.